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Fast Transient Mechanistic Studies using DRIFTS

DRIFTS is an important spectroscopic technique for investigating species adsorbed on a catalyst surface under dynamic reaction conditions. Of course, it is very important not to assume that any species that is detected by DRIFTS is automatically important or involved in the main reaction mechanism. A suitable DRIFTS apparatus must satisfy two criteria (1) the time resolution must be faster than the process that is being investigated; (2) the the reaction kinetics muct be consistent with those measured in a conventional reactor.

A commercial DRIFTS cell has been modified to improve gas flows:

 

This has allowed us to obtain excellent time response as shown below:

The red and green lines represent reactant species. The black line shows the much faster time response of the modified DRIFTS apparatus.

Similarly, the reaction kinetics measured in the DRIFTS cell show excellent agreement with conventional measurements:

 

Using this equipment to investigate the Water Gas Shift reaction, we have shown that for the most active platinum and gold catalysts the formate mechanism is not important:

Rate of CO2 formation contrasted with the rate of surface formate decomposition for Au/CeZrO4